The influence of the place-value structure of the Arabic number ...

Procedure: After being seated with their head stabilized by a chinrest, participants
were instructed to evaluate as fast and as accurate as possible whether the subsequently
displayed addition problems were solved correctly or not: When a problem was presented
together with its correct solution the right button of a response device had to be pressed by the
index finger of the right hand whereas a button press by the left index finger on a left button
indicated that a problem was presented with an incorrect solution. Then a nine-point
calibration of the eye-tracking system was conducted to maximize spatial resolution for each
participant. Thereafter, participants had to evaluate ten practice trials to familiarize with
display layout and task requirements. The experiment was set up in four blocks of 48 items
each and lasted about 45 minutes.
Analysis: All subsequent analyses exclusively incorporated data from items presented
with a correct solution probe. This restriction was necessary as incorrect solution probes may
be rejected following non-computational strategies (e.g., matching of intermediate unit sum).
Additionally, evaluation processes of incorrect probes may be driven by factors such as split
between incorrect probe and correct result which do not play a role in the evaluation of
correct solution probes as they do not even exist for these (e.g., Klein et al., 2009; Klein et al.,
submitted). Furthermore, Menon et al. (2002) were able to show that responses to correct and
incorrect probes differ even in their neural correlates: In incorrect addition problems specific
cortex areas were additionally recruited in left dorsolateral and ventrolateral prefrontal cortex
– areas usually not associated with the processing of domain specific numerical information.
Instead, these areas seem to play a role in monitoring contextual information (e.g., Cabeza,
Locantore, & Anderson, 2003; Ranganath, Johnson, & D’Esposito, 2000) and the generation
of alternative solutions to a given problem (e.g., Donohue et al., 2005; Goel & Vartarian,
2005). As we were specifically interested in processes necessary for deriving the correct
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